Git fails to build on Ubuntu Server 16.04

I configured with --enable-pthreads, and LIBS included -lpthread.

$ make V=1 gcc -I/usr/local/include -g -O2 -I. -DHAVE_ALLOCA_H -I/usr/local/include -DUSE_CURL_FOR_IMAP_SEND -I/usr/local/include -I/usr/local/include -DHAVE_PATHS_H -DHAVE_STRINGS_H -DHAVE_DEV_TTY -DHAVE_CLOCK_GETTIME -DHAVE_CLOCK_MONOTONIC -DHAVE_GETDELIM -DSHA1_HEADER='<openssl/sha.h>' -DNO_STRLCPY -DSHELL_PATH='"/bin/sh"' -DPAGER_ENV='"LESS=FRX LV=-c"' -o git-credential-store -Wl,-rpath,/usr/local/lib -L/usr/local/lib credential-store.o common-main.o libgit.a xdiff/lib.a -L/usr/local/lib -Wl,-rpath,/usr/local/lib -lz -L/usr/local/lib -Wl,-rpath,/usr/local/lib -lcrypto -lrt /usr/bin/ld: libgit.a(run-command.o): undefined reference to symbol 'pthread_sigmask@@GLIBC_2.2.5' //lib/x86_64-linux-gnu/libpthread.so.0: error adding symbols: DSO missing from command line collect2: error: ld returned 1 exit status Makefile:2053: recipe for target 'git-credential-store' failed make: *** [git-credential-store] Error 1

If the makefile is modified after 'make configure':

    find `pwd` -name Makefile -exec sed -i 's|-lrt|-lrt -lpthread|g' {} \;

Then Git builds successfully.

It appears the request to use pthreads is not being honored.

Thanks.